Light-emitting panel, display device and electronic equipment

ABSTRACT

Disclosed herein is a light-emitting panel including: an organic electroluminescence element adapted to emit electroluminescence light toward a transparent substrate; a pixel circuit formed on the transparent substrate and adapted to drive the organic electroluminescence element; a color filter formed not only between the transparent substrate and organic electroluminescence element but also immediately on or above the pixel circuit; and a conductive layer formed between the pixel circuit and color filter, the conductive layer being more conductive than the color filter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/439,001, filed Apr. 4, 2012, which claims priority to Japanese PatentApplication No. 2011-087417, filed in the Japan Patent Office on Apr.11, 2011, the entire disclosures of which are hereby incorporated hereinby reference.

BACKGROUND

The present disclosure relates to a light-emitting panel having anorganic EL (electro luminescence) element, a display device having thesame light-emitting panel and electronic equipment having the samedisplay device.

Recent years have seen the development of current-driven opticalelements such as organic EL elements for use as a light-emitting elementof a pixel and efforts undertaken to make them commercially available inthe field of display devices adapted to display an image (refer, forexample, to Japanese Patent Laid-Open No. 2008-083272). The emissionbrightness of these current-driven optical elements changes according tothe current flowing therethrough. Organic EL elements are self-luminousunlike liquid crystal elements. This eliminates the need for a displaydevice using organic EL elements (organic EL display device) to have alight source (backlight), thus providing higher image visibility, lowerpower consumption and faster element response than liquid crystaldisplay devices for which a light source is necessary.

Organic EL display devices are classified into two types, passive matrixand active matrix display devices, depending on a driving methodthereof, just as are liquid crystal display devices. The former issimpler in structure. However, it is difficult for this type of organicEL display device to grow into a large-size and high definition displaydevice. Today, therefore, increasing efforts are being made to developactive matrix models. This type of display device is designed to controlthe current flowing through the light-emitting element provided in eachof the pixels using active elements (commonly TFTs (Thin FilmTransistors) provided in a drive circuit that is provided for each ofthe light-emitting elements.

SUMMARY

Incidentally, the structure adapted to extract EL light can beclassified into two types, bottom emission and top emission structures.With the former or bottom emission structure, a color filter is formedon TFT circuitry. However, the color filter becomes charged when itreceives EL light from the organic EL element, thus changing the TFTcharacteristic because of the charge collected on the color filter.

For example, it is clear as illustrated in FIG. 16 that the TFTcharacteristic of an n-channel transistor with a color filter, providedthereon or thereabove, irradiated with EL light is different from thatwith no color filter near the n-channel transistor. More specifically,the TFT threshold voltage has moved in the negative direction, with agreater leak current in the OFF condition. If a TFT whose characteristichas undergone such a change is used as a write transistor, the chargeheld by the holding capacitor in the pixel circuit leaks during thelight emission period, thus resulting in lower brightness.

The present disclosure has been made in light of the foregoing, and itis desirable to provide a light-emitting panel that can reduce thechange in characteristic of the pixel circuit caused by the charging ofthe color filter, a display device having the same light-emitting paneland electronic equipment having the same display device.

A light-emitting panel according to an embodiment of the presentdisclosure includes an organic EL element, pixel circuit, color filterand conductive layer in each pixel. Here, the organic EL element emitsEL light toward a transparent substrate. The pixel circuit drives theorganic EL element and is formed on the transparent substrate. The colorfilter is formed not only between the transparent substrate and organicEL element but also immediately on or above the pixel circuit. Theconductive layer is made of a material more conductive than the colorfilter and formed between the pixel circuit and color filter.

A display device according to the embodiment of the present disclosureincludes the above light-emitting panel as a display panel and furtherincludes a drive circuit adapted to drive the display panel. Electronicequipment according to the embodiment of the present disclosure includesthe above display device.

In the light-emitting panel, display device and electronic equipmentaccording to the embodiment of the present disclosure, the conductivelayer more conductive than the color filter is formed between the pixelcircuit and color filter in the bottom emission light-emitting panel.This reduces the tendency of the pixel circuit to be affected by thecharging of the color filter as a result of the reception of EL lightemitted from the organic EL element.

In the present disclosure, the pixel circuit includes, for example, aholding capacitor, and first and second transistors. The firsttransistor writes a predetermined voltage to the holding capacitor. Thesecond transistor drives the organic EL element based on the voltage ofthe holding capacitor. If the pixel circuit is configured as describedabove, and if the color filter is formed immediately on or above thefirst transistor, it is preferred that the conductive layer should beformed between the first transistor and color filter.

Further, in the present disclosure, the first transistor includes, forexample, a gate, source, drain and channel. If the first transistor isconfigured as described above, it is preferred that the conductive layershould cover part of the channel of all the region of the firsttransistor opposed to the color filter. Still further, it is morepreferred that the conductive layer should cover at least the terminal,i.e., the channel, source or drain, which is externally supplied with asignal because this makes the pixel circuit less affected by thecharging of the color filter.

Still further, in the present disclosure, the first transistor may beinsulated from the conductive layer by an insulating layer forisolation. Alternatively, in the present disclosure, the conductivelayer may electrically float. Still alternatively, the conductive layermay be electrically connected to a conductive member different from theconductive layer so as to assume a predetermined potential.

In the light-emitting panel, display device and electronic equipmentaccording to the embodiment of the present disclosure, the conductivelayer more conductive than the color filter is formed between the pixelcircuit and color filter, thus reducing the change in characteristic ofthe pixel circuit caused by the charging of the color filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a display device according to anembodiment of the present disclosure;

FIG. 2 is a circuit diagram of a subpixel shown in FIG. 1;

FIG. 3 is a layout of the components of the subpixel shown in FIG. 1;

FIG. 4 is a diagram illustrating an example of cross-sectional structureof the subpixel shown in FIG. 3 as seen in the direction of arrow A-A;

FIG. 5 is a diagram illustrating an example of cross-sectional structureof the subpixel shown in FIG. 3 as seen in the direction of arrow B-B;

FIGS. 6A to 6E are diagrams illustrating examples of waveforms inrelation to the subpixel shown in FIG. 2;

FIG. 7 is a diagram illustrating another example of the cross-sectionalstructure of the subpixel shown in FIG. 3 as seen in the direction ofarrow A-A;

FIG. 8 is a plan view illustrating the schematic configuration of amodule including the display device according to a modification exampleof the embodiment;

FIG. 9 is a perspective view illustrating the appearance of applicationexample 1 of the display device according to the embodiment andmodification example thereof;

FIG. 10A is a perspective view illustrating the appearance ofapplication example 2 as seen from the front, and 10B is a perspectiveview illustrating the appearance thereof as seen from the back;

FIG. 11 is a perspective view illustrating the appearance of applicationexample 3;

FIG. 12 is a perspective view illustrating the appearance of applicationexample 4;

FIG. 13A is a front view of application example 5 in an open position,FIG. 13B is a side view thereof, FIG. 13C is a front view in a closedposition, FIG. 13D is a left side view, FIG. 13E is a right side view,FIG. 13F is a top view, and FIG. 13G is a bottom view;

FIG. 14 is a diagram illustrating an example of cross-sectionalstructure of the portion of a subpixel in related art equivalent to thatalong line A-A shown in FIG. 3;

FIG. 15 is a diagram illustrating another example of the cross-sectionalstructure of the portion of the subpixel in related art equivalent tothat along line A-A shown in FIG. 3; and

FIG. 16 is a characteristic diagram for describing the change incharacteristic of an organic EL element caused by the charging of acolor filter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A detailed description will be given below of the preferred embodimentof the present disclosure with reference to the accompanying drawings.It should be noted that the description will be given in the followingorder.

1. Embodiment

Example in which a conductive layer is provided immediately on or abovethe pixel circuit

2. Module and Application Examples 1. Embodiment Configuration

FIG. 1 illustrates an example of overall structure of a display device 1according to an embodiment of the present disclosure. The display device1 includes a display panel 10 and drive circuit 20 adapted to drive thedisplay panel 10.

The display panel 10 has a display region 10A in which a plurality ofdisplay pixels 14 are arranged two-dimensionally. The display panel 10displays an image based on an eternally fed video signal 20A by activematrix driving of each of the display pixels 14. Each of the displaypixels 14 includes a red subpixel 13R, green subpixel 13G and bluesubpixel 13B. It should be noted that the subpixels 13R, 13G and 13B arecollectively referred to as the subpixels 13 in the description givenbelow.

FIG. 2 illustrates an example of circuit configuration of the subpixel13. The subpixel 13 includes an organic EL element 11 and pixel circuit12 adapted to drive the organic EL element 11 as illustrated in FIG. 2.It should be noted that an organic EL element 11R adapted to emit red ELlight is provided as an organic EL element in the subpixel 13R.Similarly, an organic EL element 11G adapted to emit green EL light isprovided as an organic EL element in the subpixel 13G, and an organic ELelement 11B adapted to emit blue EL light is provided as an organic ELelement in the subpixel 13B.

The pixel circuit 12 is, for example, a two-transistor/one-capacitor(2Tr1C) circuit including a write transistor Tws, drive transistor Tdrand holding capacitor Cs. It should be noted that the pixel circuit 12is not limited to a two-transistor/one-capacitor circuit. Alternatively,the pixel circuit 12 may include two write transistors Tws that areconnected to each other in series. Still alternatively, the pixelcircuit 12 may include transistors or capacitors different from theabove.

The write transistor Tws writes a voltage commensurate with the videosignal 20A to the holding capacitor Cs. The drive transistor Tdr drivesthe organic EL element 11 based on the voltage of the holding capacitorCs written by the write transistor Tws. The write transistor Tws anddrive transistor Tdr include, for example, n-channel MOS (Metal OxideSemiconductor) thin film transistors (TFTs). It should be noted that thewrite transistor Tws and drive transistor Tdr may include p-channel MOSTFTs.

It should be noted that the write transistor Tws according to thepresent embodiment corresponds to a specific example of a “firsttransistor,” and that the drive transistor according to the presentembodiment corresponds to a specific example of a “second transistor.”Further, the holding capacitor Cs corresponds to a specific example of a“holding capacitor.”

The drive circuit 20 includes a timing generation circuit 21, videosignal processing circuit 22, data line drive circuit 23, gate linedrive circuit 24 and drain line drive circuit 25. The drive circuit 20also includes data lines DTL, gate lines WSL and drain lines DSL. Eachof the data lines DTL is connected to one of the outputs of the dataline drive circuit 23. Each of the gate lines WSL is connected to one ofthe outputs of the gate line drive circuit 24. Each of the drain linesDSL is connected to one of the outputs of the drain line drive circuit25. The drive circuit 20 still further includes a ground line GND (referto FIG. 2) that is connected to the cathode of the organic EL element11. It should be noted that the ground line GND is connected to theground and assumes the ground voltage when connected to the ground.

The timing generation circuit 21 controls the data line drive circuit23, gate line drive circuit 24 and drain line drive circuit 25, forexample, so that these circuits operate in concert with each other. Thetiming generation circuit 21 outputs a control signal 21A to thesecircuits, for example, in response to (in synchronism with) anexternally fed synchronizing signal 20B.

The video signal processing circuit 22, for example, corrects theexternally fed digital video signal 20A, converts the corrected videosignal into an analog signal and outputs a resultant signal voltage 22Bto the data line drive circuit 23.

The data line drive circuit 23 writes the signal voltage 22B fed fromthe video signal processing circuit 22 to the selected display pixel 14(or subpixel 13) via the data line DTL in response to (in synchronismwith) the input of the control signal 21A. The data line drive circuit23 can output, for example, two voltages, i.e., the signal voltage 22Band a constant voltage irrelevant to the video signal.

The gate line drive circuit 24 applies a selection pulse to theplurality of gate lines WSL one after another in response to (insynchronism with) the input of the control signal 21A, thus selectingthe plurality of display pixels 14 (or subpixels 13) on the gate lineWSL-by-gate line WSL basis. The gate line drive circuit 24 can output,for example, two voltages, i.e., a voltage applied to turn ON the writetransistor Tws and another applied to turn OFF the write transistor Tws.

The drain line drive circuit 25 outputs a predetermined voltage to thedrain of the drive transistor of each of the pixel circuits 12 via thedrain line DSL in response to (in synchronism with) the input of thecontrol signal 21A. The drain line drive circuit 25 can output, forexample, two voltages, i.e., a voltage applied to cause the organic ELelement 11 to emit light and another applied to cause the organic ELelement 11 to stop emitting light.

A description will be given next of the connection between thecomponents and their layout with reference to FIGS. 2 and 3. It shouldbe noted that FIG. 3 illustrates an example of layout of the componentsof the subpixel 13.

Each of the gate lines WSL is formed to extend in the row direction andconnected to a gate 31A of the write transistor Tws via a contact 37A.Each of the drain lines DSL is also formed to extend in the rowdirection and connected to a drain 32C of the drive transistor Tdr viacontacts 37B. Each of the data lines DTL is formed to extend in thecolumn direction and connected to a drain 31C of the write transistorTws via contacts 37C.

A source 31B of the write transistor Tws is connected to a gate 32A ofthe drive transistor Tdr and one end (terminal 33A) of the holdingcapacitor Cs via contacts 37D. A source 32B of the drive transistor Tdrand the other end (terminal 33B) of the holding capacitor Cs areconnected to an anode 35A of the organic EL element 11 via contacts 37E.An organic layer 35C of the organic EL element 11 is arranged in aregion on the anode 35A and not opposed to the write transistor Tws ordrive transistor Tdr. A cathode 35B of the organic EL element 11 isarranged on an organic layer 35C and connected to the ground line GND.The cathode 35B is formed, for example, over the entire surface of thedisplay region 10A.

A description will be given next of the cross-sectional structure of thewrite transistor Tws and the region close thereto in the display panel10. FIG. 4 illustrates an example of cross-sectional structure of thesubpixel 13 shown in FIG. 3 as seen in the direction of arrow A-A. Thedisplay panel 10 includes, for example, the write transistor Tws,holding capacitor Cs and data line DTL in the write transistor Tws andthe region close thereto on a substrate 41 as illustrated in FIG. 4. Thedisplay panel 10 has, for example, a gate insulating layer 42,insulating layers 43 and 44, conductive layer 45, color filter 46,insulating layers 47 and 48, the cathode 35B, an insulating layer 49 andsubstrate 50 stacked in this order from the side of the substrate 41 inthe write transistor Tws and the region close thereto as illustrated inFIG. 4.

The insulating layer 43 has openings 43A, and the display panel 10 hasthe contact 37C or 37D in each of the openings 43A. The display panel 10has a drain lead-out electrode 31E immediately on the contacts 37C. Thedrain lead-out electrode 31E is electrically connected to the data lineDTL and drain 31C via the contacts 37C. Further, the display panel 10has a source lead-out electrode 31F immediately on the contacts 37D. Thesource lead-out electrode 31F is electrically connected to the source31B and the terminal 33A of the holding capacitor Cs via the contacts37D.

The insulating layer 44 fully covers the drain lead-out electrode 31E,source lead-out electrode 31F and insulating layer 43, insulating theseelectrodes and the conductive layer 45 from each other. The conductivelayer 45 is made of a material more conductive than the color filter 46.The conductive layer 45 is made of a transparent conductive materialsuch as ITO (Indium Tin Oxide). If made of a transparent conductivematerial, the conductive layer 45 can be formed in the openings of thesubpixel 13. It should be noted that the conductive layer 45 may bemade, for example, of a metallic material. In this case, however, it ispreferred that the conductive layer 45 should be formed only immediatelyabove the write transistor Tws (or drain lead-out electrode 31E andsource lead-out electrode 31F) in such a manner as to avoid the openingsof the subpixel 13 as illustrated in FIG. 3.

The conductive layer 45 covers, for example, at least a channel 31D ofthe write transistor Tws of all the region of the write transistor Twsopposed to the color filter 46 as illustrated in FIG. 4. It is preferredthat the conductive layer 45 should cover, for example, at least thesource lead-out electrode 31F, i.e., the terminal on the opposite sideof that externally supplied with a signal, of all the region of thewrite transistor Tws opposed to the color filter 46, i.e., the channel31D, drain lead-out electrode 31E and source lead-out electrode 31F, asillustrated in FIG. 4. The conductive layer 45 is, for example, notconnected to any other conductive member and, therefore, electricallyfloats. It should be noted that the conductive layer 45 need notnecessarily electrically float. Instead, the conductive layer 45 may be,for example, electrically connected to a conductive member differentfrom the conductive layer 45 and, therefore, assume a predeterminedpotential.

The color filter 46, for example, fully covers the subpixel 13 asillustrated in FIG. 3. The color filter 46 is formed not only betweenthe substrate 41 and organic EL element 11 but also immediately abovethe pixel circuit 12. The color filter 46 is also formed, for example,immediately above the write transistor Tws as illustrated in FIG. 4. Inthe present embodiment, however, the conductive layer 45 is providedbetween the color filter 46 and write transistor Tws. Therefore, even ifthe color filter 46 becomes charged as a result of reception of EL lightfrom the organic EL element 11, the pixel circuit 12 (especially, thewrite transistor Tws) does not readily become affected by the chargingof the color filter 46.

A description will be given next of the cross-sectional structure of thedrive transistor Tdr and the region close thereto in the display panel10. FIG. 5 illustrates an example of cross-sectional structure of thesubpixel 13 shown in FIG. 3 as seen in the direction of arrow B-B. Thedisplay panel 10 includes the drive transistor Tdr, holding capacitor Csand data line DTL in the drive transistor Tdr and the region closethereto on the substrate 41 as illustrated in FIG. 4. The display panel10 has, for example, the gate insulating layer 42, insulating layers 43and 44, color filter 46, insulating layers 47 and 48, organic EL element11, insulating layer 49 and substrate 50 stacked in this order from theside of the substrate 41 in the drive transistor Tdr and the regionclose thereto as illustrated in FIG. 5.

The insulating layer 43 has the opening 43A, and the display panel 10has the contact 37C in the opening 43A. Although not shown, the displaypanel 10 has a drain lead-out electrode immediately on the contacts 37B(refer to FIG. 3). The drain lead-out electrode is electricallyconnected to the drain 32C of the drive transistor Tdr via the contacts37B. Further, the display panel 10 has a source lead-out electrode 32Eimmediately on the contacts 37E (refer to FIG. 3). The source lead-outelectrode 32E is electrically connected to the source 32B of the drivetransistor Tdr via the contacts 37E.

The anode 35A of the organic EL element 11 is connected to the sourcelead-out electrode 32E via the insulating layer 47 and an opening 47Aformed in the color filter 46. The anode 35A has a flat region formed onthe flat surface of the insulating layer 47, and the organic layer 35Cis formed in contact with the flat region of the anode 35A. The cathode35B is formed at least in contact with the top surface of the organiclayer 35C and serves, for example, as a common electrode formed over theentire surface including the organic layer 35C and insulating layer 48.

Here, the substrate 41 includes, for example, a substrate transparent toEL light such as glass or resin substrate. The substrate 50 includes,for example, a glass, silicon (Si) or resin substrate. The anode 35A ismade of a conductive material transparent to visible light such as ITO.The organic layer 35C includes, for example, a hole injection layer,hole transport layer, light-emitting layer and electron transport layerthat are stacked in this order from the side of the anode 35A. The holeinjection layer provides enhanced hole injection efficiency. The holetransport layer provides enhanced hole transport efficiency to thelight-emitting layer. The light-emitting layer emits light as a resultof the recombination of electrons and holes. The electron transportlayer provides enhanced electron transport efficiency to thelight-emitting layer. The cathode 35B is made of a metallic material andserves as a reflecting mirror. This ensures that light emitted from theorganic layer 35C of the organic EL element 11 is externally output viathe anode 35A, insulating layer 48, color filter 46, insulating layers44, 43 and 42 and substrate 41. Therefore, the rear side of thesubstrate 41 (side opposite to that on which the drive transistor Tdr isprovided) serves as a video display surface S. As a result, the displaypanel 10 has a bottom emission structure.

[Operation]

A description will be given next of an example of operation of thedisplay device 1 according to the present embodiment.

In this display device 1, the signal voltage 22B commensurate with thevideo signal 20A is applied to each of the data lines DTL by the dataline drive circuit 23. At the same time, a selection pulse commensuratewith the control signal 21A is applied to the plurality of gate linesWSL and drain lines DSL by the gate line drive circuit 24 and drain linedrive circuit 25 one after another. Practically, a picture is displayedas a result of the operation described below.

FIGS. 6A to 6E illustrate examples of waveforms of the voltages appliedto the pixel circuit 12 and examples of changes in a gate voltage Vg andsource voltage Vs of the drive transistor Tdr. FIG. 6A illustrates asignal voltage Vsig and offset voltage Vofs applied to the data lineDTL. FIG. 6B illustrates voltages Von and Voff applied to the gate lineWSL. The voltage Von turns ON the write transistor Tws, and the voltageVoff turns OFF the write transistor Tws. FIG. 6C illustrates voltagesVcc and Vini applied to the drain line DSL. Further, FIGS. 6D and 6Eillustrate the moment-to-moment changes in the gate voltage Vg andsource voltage Vs of the drive transistor Tdr in response to theapplication of the voltages to the drain line DSL, data line DTL andgate line WSL.

(Preparation Period for Threshold Correction)

First, preparations are made for the threshold correction. Morespecifically, when the voltage of the gate line WSL is at Voff, and thatof the drain line DSL is at Vcc (that is, when the organic EL element 11emits light), the drain line drive circuit 25 brings the voltage of thedrain line DSL from Vcc down to Vini (T1). As a result, the sourcevoltage Vs drops to Vini, causing the organic EL element 11 to stopemitting light. Then, when the voltage of the data line DTL is at Vofs,the gate line drive circuit 24 brings the voltage of the gate line WSLfrom Voff up to Von, changing the gate voltage of the drive transistorTdr to Vofs.

(First Threshold Correction Period)

Next, the threshold correction is performed. More specifically, when thewrite transistor Tws is ON, and the voltage of the data line DTL is atVofs, the drain line drive circuit 25 brings the voltage of the drainline DSL from Vini up to Vcc (T2). As a result, a current Ids flows fromthe drain to source of the drive transistor Tdr, thus raising the sourcevoltage Vs. Then, before the data line drive circuit 23 changes thevoltage of the data line DTL from Vofs to Vsig, the gate line drivecircuit 24 brings the voltage of the gate line WSL from Von down to Voff(T3). This causes the gate of the drive transistor Tdr to float, thuscausing the threshold correction to pause.

(First Pause Period of the Threshold Correction)

During a pause period of the threshold correction, for example, thevoltage of the data line DTL is sampled in a row different from that(pixel) which underwent the threshold correction. It should be notedthat, at this time, the source voltage Vs is lower than Vofs-Vth (whereVth is the threshold voltage of the drive transistor Tdr) in the row(pixel) which underwent the threshold correction. During a pause periodof the threshold correction, therefore, the current Ids flows from thedrain to source of the drive transistor Tdr in the row (pixel) whichunderwent the threshold correction, thus raising not only the sourcevoltage Vs but also the gate voltage Vg because of the coupling via theholding capacitor Cs.

(Second Threshold Correction Period)

Next, the threshold correction is performed again. More specifically,when the pixel circuit 12 is ready for threshold correction because thevoltage of the data line DTL is at Vofs, the gate line drive circuit 24brings the voltage of the gate line WSL from Voff up to Von, changingthe gate voltage of the drive transistor Tdr to Vofs (T4). At this time,if the source voltage Vs is lower than Vofs-Vth (if the thresholdcorrection has yet to be complete), the current Ids flows from the drainto source of the drive transistor Tdr until the drive transistor Tdrgoes into cutoff (until a gate-to-source voltage Vgs reaches Vth). Then,before the data line drive circuit 23 changes the voltage of the dataline DTL from Vofs to Vsig, the gate line drive circuit 24 brings thevoltage of the gate line WSL from Von down to Voff (T5). This causes thegate of the drive transistor Tdr to float, thus maintaining thegate-to-source voltage Vgs constant irrespective of the magnitude of thevoltage of the data line DTL.

It should be noted that if, during the threshold correction period, theholding capacitor Cs is charged to Vth, and therefore, thegate-to-source voltage Vgs reaches Vth, the drive circuit 20 terminatesthe threshold correction. However, if the gate-to-source voltage Vgsdoes not reach Vth, the drive circuit 20 repeats the thresholdcorrection and pause until the gate-to-source voltage Vgs reaches Vth.

(Writing and Mobility Correction Period)

The pause period of the threshold correction is followed by the writingand mobility correction. More specifically, when the voltage of the dataline DTL is at Vsig, the gate line drive circuit 24 brings the voltageof the gate line WSL from Voff up to Von (T6), connecting the gate ofthe drive transistor Tdr to the data line DTL. This brings the gatevoltage Vg of the drive transistor Tdr equal to the voltage Vsig of thedata line DTL. At this time, the anode voltage of the organic EL element11 is still smaller than a threshold voltage Vel of the organic ELelement 11. Therefore, the organic EL element 11 is still in cutoff. Asa result, the current Ids flows into the element capacitance (not shown)of the organic EL element 11, thus charging the element capacitance.This raises the source voltage Vs by ΔV, thus bringing thegate-to-source voltage Vgs equal to Vsig+Vth−ΔV before long. The writingand mobility correction are performed at the same time as describedabove. Here, the greater the mobility of the drive transistor Tdr, thegreater ΔV. Therefore, the variation in mobility between the subpixels13 can be eliminated by reducing the gate-to-source voltage Vgs by ΔVbefore light emission.

(Bootstrapping Period)

Finally, the gate line drive circuit 24 brings the voltage of the gateline WSL from Von down to Voff (T7). This causes the gate of the drivetransistor Tdr to float, thus causing the current Ids to flow from thedrain to source of the drive transistor Tdr and raising the sourcevoltage Vs. As a result, a voltage greater than the threshold voltageVel is applied to the organic EL element 11, thus causing the organic ELelement 11 to emit light at a desired brightness.

As described above, in the display device 1 according to the presentembodiment, the pixel circuit 12 is controlled to turn ON and OFF ineach of the subpixels 13. As a result, a drive current is injected intothe organic EL element 11 of each of the subpixels 13. This recombinesholes and electrons followed by light emission, after which emittedlight is externally extracted. As a result, an image is displayed in thedisplay region 10A of the display panel 10.

[Effect]

A description will be given next of the effect of the display device 1according to the present embodiment.

In general, if the display device is a bottom emission display devicefor extraction of EL light, a color filter is formed on or above the TFTcircuitry. As illustrated in FIG. 14, for example, the color filter 46is directly in contact with the drain lead-out electrode 31E and sourcelead-out electrode 31F. Alternatively, as illustrated in FIG. 15, forexample, the color filter 46 is in contact with the drain lead-outelectrode 31E and source lead-out electrode 31F via the thin insulatinglayer 44. However, the color filter becomes charged when it receives ELlight from the organic EL element, thus changing the TFT characteristicbecause of the charge collected on the color filter.

For example, it is clear as illustrated in FIG. 16 that the TFTcharacteristic of an n-channel transistor with a color filter, providedthereon or thereabove, irradiated with EL light is different from thatwith no color filter near the n-channel transistor. More specifically,the TFT threshold voltage has moved in the negative direction, with agreater leak current in the OFF condition. If a TFT whose characteristichas undergone such a change is used as a write transistor, the chargeheld by the holding capacitor in the pixel circuit leaks during thelight emission period, thus resulting in lower brightness.

In the present embodiment, on the other hand, the conductive layer 45more conductive than the color filter 46 is formed between the pixelcircuit 12 and color filter 46 in the bottom emission display panel 10.This ensures that even if the color filter 46 becomes charged as aresult of reception of EL light from the organic EL element 11, thepixel circuit 12 does not readily become affected by the charging of thecolor filter 46. This can reduce the change in characteristic of thewrite transistor Tws caused by the charging of the color filter 46.

Modification Example

In the above embodiment, the conductive layer 45 covers at least thechannel 31D of the write transistor Tws of all the region of the writetransistor Tws opposed to the color filter 46. However, the conductivelayer 45 need only cover at least part of the channel 31D of the writetransistor Tws of all the region of the write transistor Tws opposed tothe color filter 46. As illustrated in FIG. 7, for example, theconductive layer 45 need only cover part of the channel 31D of all theregion of the write transistor Tws opposed to the color filter 46. Evenin such a case, the change in the characteristic of the write transistorTws caused by the charging of the color filter 46 can be reduced ascompared to the absence of the conductive layer 45.

2. Module and Application Examples

A description will be given below of application examples of the displaydevice 1 described in the above embodiment and modification example. Thedisplay device 1 is applicable to electronic equipment across alldisciplines adapted to display a video signal fed thereto or generatedtherein as an image or picture. Among examples of electronic equipmentare television set, digital camera, laptop personal computer, personaldigital assistance such as mobile phone and video camcorder.

[Module]

The display device 1 is built into a variety of electronic equipmentincluding application examples 1 to 5 as a module as shown, for example,in FIG. 8. This module is manufactured, for example, as follows. Thatis, a region 210 exposed from a member (not shown) adapted to seal thedisplay panel 10 is provided on one side of a substrate 3. Then, theinterconnects of the timing generation circuit 21, video signalprocessing circuit 22, data line drive circuit 23, gate line drivecircuit 24 and drain line drive circuit 25 are extended to this exposedregion 210, thus forming external connection terminals (not shown). AnFPC (flexible printed circuit) 220 adapted to exchange signals may beprovided on the external connection terminals.

Application Example 1

FIG. 9 illustrates the appearance of a television set to which thedisplay device 1 is applied. This television set has, for example, avideo display screen section 300 including a front panel 310 and filterglass 320. The video display screen section 300 includes the displaydevice 1.

Application Example 2

FIGS. 10A and 10B illustrate the appearance of a digital camera to whichthe display device 1 is applied. This digital camera has, for example, aflash-emitting section 410, display section 420, menu switch 430 andshutter button 440. The display section 420 includes the display device1.

Application Example 3

FIG. 11 illustrates the appearance of a laptop personal computer towhich the display device 1 is applied. This laptop personal computerhas, for example, a main body 510, keyboard 520 adapted to bemanipulated for entry of text or other information and a display section530 adapted to display an image. The display section 530 includes thedisplay device 1.

Application Example 4

FIG. 12 illustrates the appearance of a video camcorder to which thedisplay device 1 is applied. This video camcorder has, for example, amain body section 610, lens 620 provided on the front-facing sidesurface of the main body section 610 to capture the image of thesubject, imaging start/stop switch 630 and display section 640. Thedisplay section 640 includes the display device 1.

Application Example 5

FIGS. 13A to 13G illustrate the appearance of a mobile phone to whichthe display device 1 is applied. This mobile phone is made up, forexample, of an upper enclosure 710 and lower enclosure 720 that areconnected together with a connecting section (hinge section) 730 and hasa display 740, subdisplay 750, picture light 760 and camera 770. Thedisplay 740 or subdisplay 750 includes the above display device 1.

Although described above with reference to the preferred embodiment andapplication examples, the present disclosure is not limited thereto andmay be modified in various ways.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

In the above embodiment and others, for example, a case has beendescribed in which the present disclosure is applied to a displaydevice. However, the present disclosure is applicable, for example, to alighting device.

Further, a case has been described in the above embodiment and others inwhich the display device is an active matrix display device. However,the configuration of the pixel circuit 12 adapted to achieve activematrix driving is not limited to that described in the presentembodiment. Therefore, it is possible to add capacitive elements andtransistors to the pixel circuit 12 as necessary. In this case, anecessary drive circuit may be added in addition to the timinggeneration circuit 21, video signal processing circuit 22, data linedrive circuit 23, gate line drive circuit 24 and drain line drivecircuit 25 to accommodate the changes made to the pixel circuit 12.

Still further, in the above embodiment and others, the timing generationcircuit 21 and video signal processing circuit 22 control the drivingperformed by the data line drive circuit 23, gate line drive circuit 24and drain line drive circuit 25. However, other circuits may control thedriving. On the other hand, the data line drive circuit 23, gate linedrive circuit 24 and drain line drive circuit 25 may be controlled byhardware (circuitry) or software (program).

Still further, in the above embodiment and others, a description hasbeen given assuming that the source and drain of the write transistorTws and those of the drive transistor Tdr are fixed. It is, however,needless to say that the source-drain orientation may be reversed fromthat described above depending on the current flow direction.

Still further, in the above embodiment and others, a description hasbeen given assuming that the write transistor Tws and drive transistorTdr include n-channel MOS TFTs. However, at least one of the writetransistor Tws and drive transistor Tdr may include a p-channel MOS TFT.It should be noted that if the drive transistor Tdr includes a p-channelMOS TFT, the anode 35A of the organic EL element 11 serves as a cathode,and the cathode 35B thereof as an anode in the above embodiment andothers. Still further, in the above embodiment and others, the writetransistor Tws and drive transistor Tdr need not necessarily includeamorphous silicon TFTs or micro-silicon TFTs. Instead, the sametransistors Tws and Tdr may include low-temperature polysilicon TFTs.

What is claimed is:
 1. A light-emitting panel comprising: an organicelectroluminescence element; a pixel circuit; a color filter; and aconductive layer, wherein the pixel circuit is disposed on a transparentsubstrate and includes a holding capacitor, a first transistor connectedto the holding capacitor, and a second transistor connected to theorganic electroluminescence element, the color filter is disposedbetween the first transistor and the organic electroluminescenceelement, and the conductive layer is disposed between the firsttransistor and the color filter.
 2. The light-emitting panel of claim 1,wherein the first transistor has a gate, source, drain and channel, andthe conductive layer covers part of the channel of all of a region ofthe first transistor opposed to the color filter.
 3. The light-emittingpanel of claim 1, wherein the first transistor is insulated from theconductive layer by an insulating layer for isolation.
 4. Thelight-emitting panel of claim 1, wherein the conductive layerelectrically floats.
 5. The light-emitting panel of claim 1, wherein theconductive layer is electrically connected to a conductive memberdifferent from the conductive layer so as to assume a predeterminedpotential.
 6. The light-emitting panel of claim 1, wherein thelight-emitting panel has a bottom emission structure.
 7. A displaydevice comprising: a display panel; and a drive circuit adapted to drivethe display panel, wherein, the display panel includes an organicelectroluminescence element, a pixel circuit, a color filter, and aconductive layer, the pixel circuit is disposed on a transparentsubstrate and includes a holding capacitor, a first transistor connectedto the holding capacitor, and a second transistor connected to theorganic electroluminescence element, the color filter is disposedbetween the first transistor and the organic electroluminescenceelement, and the conductive layer is disposed between the firsttransistor and the color filter.
 8. The display device of claim 7,wherein the first transistor has a gate, source, drain and channel, andthe conductive layer covers part of the channel of all of a region ofthe first transistor opposed to the color filter.
 9. The display deviceof claim 7, wherein the first transistor is insulated from theconductive layer by an insulating layer for isolation.
 10. The displaydevice of claim 7, wherein the conductive layer electrically floats. 11.The display device of claim 7, wherein the conductive layer iselectrically connected to a conductive member different from theconductive layer so as to assume a predetermined potential.
 12. Thedisplay device of claim 7, wherein the display panel has a bottomemission structure.
 13. An electronic apparatus including the displaydevice of claim
 7. 14. A light-emitting panel comprising: an organicelectroluminescence element; a color filter disposed between atransistor and the organic electroluminescence element; and a conductivelayer disposed between the transistor and the color filter.
 15. Anelectronic apparatus including the light-emitting panel of claim 14.